Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752129AbbFMHs6 (ORCPT ); Sat, 13 Jun 2015 03:48:58 -0400 Received: from mail-wi0-f179.google.com ([209.85.212.179]:34094 "EHLO mail-wi0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751230AbbFMHsu (ORCPT ); Sat, 13 Jun 2015 03:48:50 -0400 Date: Sat, 13 Jun 2015 09:48:44 +0200 From: Ingo Molnar To: Oleg Nesterov Cc: linux-kernel@vger.kernel.org, linux-mml@vger.kernel.org, Andy Lutomirski , Andrew Morton , Denys Vlasenko , Brian Gerst , Peter Zijlstra , Borislav Petkov , "H. Peter Anvin" , Linus Torvalds , Thomas Gleixner , Waiman Long Subject: Re: [PATCH 02/12] x86/mm/hotplug: Remove pgd_list use from the memory hotplug code Message-ID: <20150613074844.GC30388@gmail.com> References: <1434031637-9091-1-git-send-email-mingo@kernel.org> <1434031637-9091-3-git-send-email-mingo@kernel.org> <20150612231518.GC24699@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150612231518.GC24699@redhat.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1880 Lines: 57 * Oleg Nesterov wrote: > On 06/11, Ingo Molnar wrote: > > > > void sync_global_pgds(unsigned long start, unsigned long end, int removed) > > { > > @@ -169,29 +169,33 @@ void sync_global_pgds(unsigned long start, unsigned long end, int removed) > > > > for (address = start; address <= end; address += PGDIR_SIZE) { > > const pgd_t *pgd_ref = pgd_offset_k(address); > > - struct page *page; > > + struct task_struct *g, *p; > > > > /* > > - * When it is called after memory hot remove, pgd_none() > > - * returns true. In this case (removed == 1), we must clear > > - * the PGD entries in the local PGD level page. > > + * When this function is called after memory hot remove, > > + * pgd_none() already returns true, but only the reference > > + * kernel PGD has been cleared, not the process PGDs. > > + * > > + * So clear the affected entries in every process PGD as well: > > */ > > if (pgd_none(*pgd_ref) && !removed) > > continue; > > > > spin_lock(&pgd_lock); > > - list_for_each_entry(page, &pgd_list, lru) { > > - pgd_t *pgd; > > + > > + for_each_process_thread(g, p) { > > + pgd_t *pgd = p->mm->pgd; > > and we use the same pgd later: set_pgd(pgd, *pgd_ref). > looks like this should be pgd_offset(p->mm, address) ? > > And obviously you need to check ->mm != NULL first? Yes. > And perhaps it makes sense to swap "for (address)" and for_each_process() > loops... Yes, but I'd flip around the logic in a later, separate patch. Note that PGDIR_SIZE is 512 GB here, so the outer loop will most likely execute at most twice in practice. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/